1. Field of the Invention
The present invention relates to a semiconductor device and its designing method, and more particularly, to the improvement of a layout of input/output (I/O) blocks.
2. Description of the Related Art
A first prior art semiconductor device includes an internal circuit provided in an internal circuit area; I/O blocks provided in I/O areas surrounding the internal circuit area, with each of the input/output blocks being connected by first conductive layers to the internal circuit. Pads are provided in outer areas of the input/output areas, with each of the pads being connected by a second conductive layer to one of the input/output blocks. The I/O blocks are arranged in series in one row. This will be explained later in detail.
In the above-described first prior art semiconductor device, however, because the I/O blocks are arranged in one row within the I/O areas, the pitch of the is the same as that of the I/O blocks. Therefore, when the number of the pads is changed to alter the pitch of the pads, the configuration of each of the I/O blocks has to be changed. This makes the design of semiconductor devices more complex. Thus, if the pitch of the pads is changed, I/O blocks have to be redesigned, which increases the manufacturing cost.
In a second prior art semiconductor device (see FIG. 3 in JP-A-4-127556), two rows of I/O blocks are provided in the I/O areas. Therefore, the I/O blocks can be used without changing the configuration thereof in some kinds of semiconductor devices. This also will be explained later in detail.
In the above-described second prior art semiconductor device, however, there are limited kinds of semiconductor devices to which the same I/O blocks can be applied. This makes the design of semiconductor devices more complex.
It is an object of the present invention to simplify the design of I/O blocks of semiconductor devices.
According to the present invention, in a semiconductor device including an internal circuit provided in an internal circuit area; I/O blocks provided in I/O areas surrounding the internal circuit areas, each of the input/output blocks being connected by first conductive layers to the internal circuit; and pads provided in outer areas of the input/output areas, each of the pads being connected by a second conductive layer to one of the input/output blocks, the configuration of each of the input/output blocks is fixed regardless of the pitch of the pads, and the number of rows of the input/output blocks in the input/output areas is changed in accordance with the pitch of the pads.